Emulsion aggregation (EA) is one of the many processes used for the preparation of toners. Emulsion aggregation toners may be used in forming print and/or xerographic images. Emulsion aggregation techniques may first involve the formation of a latex of the resin particles by heating the resin using a batch or semi-continuous emulsion polymerization, as disclosed in, for example, U.S. Pat. No. 5,853,943, the disclosure of which is hereby incorporated by reference in its entirety. Other examples of emulsion/aggregation/coalescing processes for the preparation of toners are illustrated in U.S. Pat. Nos. 5,902,710; 5,910,387; 5,916,725; 5,919,595; 5,925,488; 5,977,210; 5,994,020; and 7,858,285, the disclosures of each of which are hereby incorporated by reference in their entirety.
Polyester EA ultra low melt (ULM) toners have been prepared utilizing amorphous and crystalline polyester resins as illustrated, for example, in U.S. Pat. No. 7,547,499, the disclosure of which is hereby incorporated by reference in its entirety. The EA process requires polyesters to be first formulated into latex emulsions, for example, by solvent containing batch processes, such as solvent flash emulsification and/or solvent-based phase inversion emulsification (PIE).
In PIE, polyester resins are typically converted into a latex by dissolving the polyester resin in at least one organic solvent, which then needs to be removed, sometimes referred to as skipped, via a vacuum distillation process for safety and environmental concerns. However, due to stability issues during the PIE process and during transportation and storage, product loss can occur. For example, a polyester latex may gel inside the reactor and thus not form, or may form but settle out during transportation and storage. Accordingly, what is desired is an improved PIE process for latex production in which the polyester latex is reliably produced and in which the resulting latex has good stability.